1. Field of the Invention
The present invention relates to a gas-phase growing method used for the manufacture of semiconductor devices, and also to the apparatus employed for the method.
2. Description of the Related Art
In a conventional CVD apparatus which is in general use, a mixture of a raw gas and a carrier gas is made to flow onto a heated substrate inside a reaction container at a constant rate. An unconverted raw gas is discharged from the reaction container together with the carrier gas. Normally, the CVD apparatus is operated under a constant pressure so as not to disturb the gas stream inside the reaction container.
If a mixed gas containing silane and oxygen is used in the above type of CVD apparatus so as to grow silica (SiO) in a silicon submicron trench (which has come to assume importance in the field of semiconductor devices, such as DRAMs), the problem shown in FIG. 13 occurs. As is shown in FIG. 13, silica 106 grows thick at the inlet 104a of a trench 104 of a substrate 102, while it grows thin in the inside 104b of the trench 104. As a result, a void 105 is left in the inside 104b of the trench 104.
The above problem is related to the size of the trench. If a trench in the substrate is small, like a submicron trench, then the molecules of a gas repeatedly collide against the trench wall when they diffuse into the inside of the trench. Even if a void is not produced, the top surface of the silica formed to fill the trench becomes uneven. A wire cannot be easily connected to such an uneven surface. In addition, H.sub.2 O, produced by the reaction between the silane and the oxygen, remains inside the trench, adversely affecting the quality of the resultant semiconductor device.
Recently, it is reported that the problem shown in FIG. 13 can be solved by using a combination of both tetra ethoxyl silane (TEOS) and ozone as a raw gas. Even if this method is effective in solving the problem, the effect is limited to the case where SiO is grown. The method does not provide any guarantee of solution to the problem if a different material, such as SiN is grown.
With the conventional gas-phase growing method and apparatus mentioned above, it is difficult to fill the minute trenches of an uneven-surface substrate with the same or different materials, or flatten the uneven surface of that substrate.